Device and method for injecting a mixing gas into an exhaust line

ABSTRACT

A device for injecting a mixing gas into an exhaust gas exhaust line of an engine, the device comprising: one or more inlet openings, a plurality of walls comprising: o a first wall (31) and; o a second wall (32) having one or more outlet openings and being arranged downstream of the first wall, and means (36) for injecting the mixing gas between the first wall and the second wall, so as to allow the mixing gas and the exhaust gases to be mixed between the first wall and the second wall.

FIELD OF THE INVENTION

The invention relates generally to the injection of a mixing gas, and inparticular to a device for injecting, for example into an exhaust gasexhaust line of an engine. The invention also relates to a relatedassembly, exhaust line and method.

PRIOR ART

Emissions of pollutants connected with transportation have been, fornearly thirty years, a leading progress driver of the industry. Thegradual increase in the severity of the emission limits for the fourregulated pollutants (CO, HC, NO_(x), particles) has allowed asignificant improvement in air quality, particularly in large urbanareas.

The constantly increasing use of the automobile requires continuingefforts to reduce still further these pollutant emissions. Having highlyeffective remediation technologies available under all drivingconditions is thus a major challenge for the transportation industry. Inthis context, the reduction of nitrogen oxides (NO_(x)) in a leanmixture, i.e. in a mixture having an excess of oxygen, represents animportant challenge associated with a complex problem set.

Moreover, the consumption of fuel, directly connected with CO₂emissions, has been driven in a few years to the level of a majorautomobile concern. Thus, regulations have been put in place at theEuropean level beginning in 2012 regarding the CO₂ emissions of privatevehicles. It is confirmed as of now that this limit will be regularlyreduced during the coming decades. The reduction of CO₂ emissions hasthus been imposed as the new progress driver for the entiretransportation industry.

This dual problem of reducing local pollution (NO_(x)) and reducing fuelconsumption (CO₂) is particularly difficult to resolve for the Dieselengine, whose combustion of lean mixtures is accompanied by NO_(x)emissions that are difficult to treat.

In this context, the technology of SCR (“selective catalytic reduction”)post-treatment is used both in private vehicles and in vehicles assignedto the transportation of merchandise. It is then possible to positionthe engine for its optimal efficiency operation, the strong NO_(x)emissions then being treated in the exhaust by the SCR system, allowinga highly effective reduction of NO_(x).

SCR involves mixing an agent, for example a gas or a liquid, inparticular a reducing agent such as a reducing gas, for example gaseousammonia, with the exhaust gases and having the mixture pass in or over acatalyst placed in the exhaust line.

In the catalyst, the reducing agent transforms the nitrogen oxides intonitrogen and water. When the reducing agent is ammonia, NH₃, thereaction is the following:

4 NO+4 NH₃+O₂=4 N₂+6 H₂O

It is possible to inject a urea solution (hence a liquid), which istransformed into ammonia under the influence of the heat of the exhaustgases.

An aqueous solution of urea adopted and standardized for the operationof SCR systems currently in series production is designated AUS32 (thecommercial name in Europe being Adblue

This very effective method suffers however from a certain number ofdisadvantages. It has limited effectiveness when cold, while such asituation occurs in several cases, particularly that of city buses. Theurea reservoir has a considerable mass and volume, typically 15 to 30 Lfor a private vehicle, 40 to 80 L for a heavy cargo vehicle. Such a bulkcauses complexity in integration into the vehicle that is greater if thevehicle is small. A high remediation cost results, as well as excessmass which is at the expense of the fuel consumption of the vehicle andtherefore of CO₂ emissions.

The reducing agent can be injected in the form of a mixing gas. This ispossible for example by storing the reducing agent, ammonia for example,in solid form, for example by absorbing the gas inside a material, asalt for example. The storage of the gas, ammonia for example, is thenaccomplished within the salt by the formation of a chemical complex ofthe ammine type.

The storage of mixing gas, for example a reducing agent, in the form ofabsorbed gas, has the advantage of a gain in volume with respect to aliquid, for example an aqueous solution, as well as increasedeffectiveness when cold, and greater compactness of the mixing zone withthe exhaust gases, in particular.

If the agent is injected in the form of a mixing gas, it is difficult tomix it with the exhaust gas, which risks harming the effectiveness ofthe reaction of interest, SCR for example. A mixer can be positioneddownstream of the injection, but the effectiveness of known devicesremains limited.

Another problem associated with the injection of gas, for examplegaseous ammonia, into the exhaust line, arises from the increasing bulkin the line as elements (catalysts, filter, injector, sensors, etc.) areadded to it. This limits the possibilities for creating the elementsnecessary for a reaction, SCR for example.

SUMMARY OF THE INVENTION

One goal of the invention is to make more compact the elementsassociated with the injection and the mixing of gases along the exhaustline.

To this end, a device for injecting a mixing gas into an exhaust gasexhaust line of an engine is provided for, the device comprising forexample:

-   -   one or more inlet openings,    -   a plurality of walls comprising:        -   a first wall, and        -   a second wall having one or more outlet openings positioned            downstream of the first wall, and    -   means for injecting mixing gas between the first wall and the        second wall,        so as to allow mixing of the mixing gas and the exhaust gas        between the first wall and the second wall.

Such a device is particularly compact. In particular, it no longerrequires a mixer downstream of the injection, the injection deviceensuring mixing of the mixing gas and the exhaust gases. In addition,the mixing is particularly effective.

The invention is advantageously completed by the following features,taken alone or in any of their technically possible combinations:

-   -   the plurality of walls comprises at least one intermediate wall        positioned between the first wall and the second wall, the        intermediate wall comprising one or more openings;    -   means for bypassing at least one zone, at one opening at least,        configured to form a fluid communication between at least one        opening of one wall of the plurality of walls upstream of the        zone with at least one opening of a wall of the plurality of        walls downstream of the zone without passing through the zone;    -   a lateral wall connecting the first wall and the second wall and        delimiting, with the first wall, and the second wall, an        interior space,    -   the injection device is adapted to be positioned in the interior        of the exhaust line, so as to allow the passage of exhaust gas        between the lateral wall and the wall of the exhaust line;    -   the lateral wall is distinct from the wall of the exhaust line;    -   the device comprises means of attaching the device to the        exhaust line;    -   the device forms a section of the exhaust line,    -   the lateral wall is in contact with the exhaust line and/or        forms a portion of the wall of the exhaust line;    -   mixing gas supply means of the injection means,    -   the attachment means comprise the supply means;    -   the first wall and/or the lateral wall has one or more inlet        openings.    -   the injection means are positioned at the first wall and/or        extend between the first wall and the second wall from the first        wall;    -   for at least one wall of the plurality of walls, the dimensions        of the openings and/or the total empty surface and/or the total        empty surface density and/or the total empty volume density        and/or the quantity of openings vary(ies);    -   the dimensions of the openings and/or the total empty surface        and/or the total empty surface density and/or the total empty        volume density and/or the quantity of openings of at least one        wall vary(ies) with respect to at least one other wall of the        plurality of walls.

The invention also relates to an exhaust line comprising such a device.

The invention also relates to an assembly comprising an engine and anexhaust system and/or line, the assembly comprising such a device.

The invention is advantageously completed by the followingcharacteristics, taken alone or in any one of their technically possiblecombinations:

-   -   a selective catalytic reduction system for exhaust gases, and/or        an oxidation catalyst

The invention also relates to a vehicle comprising such a device and/orsuch an exhaust line and/or such an assembly.

The invention also relates to a method of a mixing gas into an exhaustgas exhaust line of an engine implemented by means of such a device,comprising the following steps:

-   -   entry of the exhaust gases between the first wall and the second        wall,    -   injection of the mixing gas between the first wall and the        second wall,    -   mixing the entered exhaust gases and the injected mixing gas, -        output of the mixed exhaust gases and mixing gas by at least one        opening of the second wall.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the invention will appear during thedescription hereafter of an embodiment. In the appended drawings:

FIG. 1 shows schematically an exhaust line according to one example ofan embodiment of the invention,

FIG. 2 shows schematically a heat engine equipped with a selectivecatalytic reduction system for exhaust gases of an engine according toone example of an embodiment of the invention,

FIGS. 3a, 3b and 3c show schematically side, front and rear views of aninjection device according to one example of an embodiment of theinvention,

FIG. 4 shows schematically a perspective view of an injection deviceaccording to another example of an embodiment of the invention,

FIG. 5 shows schematically a perspective view of an injection deviceaccording to still another example of an embodiment of the invention,

FIGS. 6a, 6b and 6c show schematically walls according to examples ofembodiments of the invention,

FIG. 7 shows schematically a side view of an injection device accordingto another example of an embodiment of the invention,

FIG. 8 shows schematically an injection method according to stillanother example of an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION Exhaust Line and Assembly

With reference to FIG. 1, an exhaust gas exhaust line of an engine 1 isdescribed, the exhaust line comprising a device for injecting a mixinggas into an exhaust gas exhaust line of an engine as describedhereafter. Alternatively or in addition, an assembly comprising such anengine and/or such an exhaust line is described, the assembly comprisingthe injection device. Alternatively or in addition, a vehicle comprisingsuch an exhaust line or such an assembly is described. The exhaust linecomprises for example a wall.

For example, the mixing gas is or comprises a reducing gas, or isconstituted essentially of a reducing gas. The reducing gas is forexample gaseous ammonia and/or gaseous hydrogen. The mixing gas is orcomprises oxygen for example.

The engine 1 is for example a heat engine. The heat engine can be aninternal-combustion engine, for example a diesel engine, or a gasolineengine with a lean mixture, such as a direct injection engine with astratified charge.

The engine 1 is for example equipped with a selective catalyticreduction system for exhaust gases, for example by means of a reducinggas, for example gaseous ammonia and/or hydrogen, as describedhereafter.

The exhaust line or the assembly is for example configured so that, atthe output of the engine 1, the exhaust gases 12 originating in theengine are for example directed toward a remediation system 2. Theexhaust line or the assembly comprises for example the remediationsystem 2. The remediation system 2 can comprise an oxidation catalyst,for example a diesel oxidation catalyst, and/or a three-way catalyst.The remediation system 2 can also comprise a particle filter.

A device 3 for injecting mixing gas, for example ammonia and/or hydrogenand/or gaseous oxygen, into an exhaust gas exhaust line of an engine asdescribed hereafter is for example positioned downstream of the outletof the engine 1, for example downstream or upstream of the remediationsystem 2. The exhaust line or the assembly comprises for example thedevice 3.

What is meant by downstream is the flow direction of the exhaust gassesalong the exhaust line, i.e. in the direction extending from the enginetoward the exhaust outlet.

What is meant by upstream is the direction opposite to the flow ofexhaust gases along the exhaust line, i.e. in the direction extendingfrom the exhaust outlet toward the engine.

The device 3 allows injecting mixing gas at the exhaust line of theengine and mixing it with the exhaust gases. The device 3 allows forexample forming a mixing gas/exhaust gas mixture 13. An additional mixer(not shown) can for example be added downstream of the device to furthermix the mixing gas with the exhaust gases. However, the device 3 alreadyallows mixing and the mixer is therefore no longer necessary, or canhave its dimensions strongly reduced.

At least at the device 3, the exhaust line comprises a portion having asection in which the exhaust gases flow, this section being delimited bya wall of the exhaust line.

An SCR catalytic converter 4 can for example be positioned downstream ofthe device, for example downstream of the mixer. The exhaust line or theassembly comprises for example the SCR catalytic converter. The SCRcatalytic converter is thus adapted for the mixing gas/exhaust gasmixture to pass through it. The SCR catalytic converter 4 is for exampleadapted to allow the reduction of the NOx by the mixing gas. The device3 can for example form an SCR catalytic converter, so that the SCRcatalytic converter can be omitted or be of reduced size.

At least one complementary post-treatment element 5, for example aplurality of such elements, can be positioned downstream of the SCRcatalytic converter 4. The exhaust line or the assembly comprises forexample the complementary element 5. The complementary element 5 cancomprise a particle filter or an oxidation catalyst. The exhaust gasesthus appear in the form of remediated exhaust gases 14 at the outlet ofthe complementary element 5. Alternatively or in addition, the SCRcatalytic converter can comprise the complementary element 5. The SCRcatalytic converter 4 can thus for example comprise a particle filter,in particular a diesel particle filter (DPF), so as to form an SCRcatalytic converter with filter (SCRF, or “selective catalytic reactionon filter”). It is thus possible to accomplish an additional spacesaving by creating an exhaust line or a system without a complementaryelement 5 or with a complementary element 5 of reduced size.

The line can comprise an exhaust outlet 17 positioned downstream of thedevice 3, for example downstream of the SCR catalytic converter 4, forexample downstream of the complementary element 5. The remediatedexhaust gases are for example then directed toward the exhaust outlet17. Thus the exhaust comprises, positioned from upstream on the engine 1side, to downstream on the outlet 17 side, for example the remediationelement 2, the device 3, for example the SCR catalytic converter 4, andfor example the complementary element 5.

System and Assembly

With reference to FIG. 2, a system is described, for example a selectivecatalytic reduction system, for exhaust gases of such an engine 1,comprising such an injection device as described hereafter.Alternatively or additionally, an assembly comprising such an engine andsuch a system is described. Alternatively or additionally, a vehiclecomprising such a system or such an assembly is described.

The engine 1 is for example controlled by an electronic computer 11. Thesystem or the assembly comprises for example the electronic computer 11.

The system or the assembly can comprise a storage enclosure 8 for mixinggas, for example ammonia and/or gaseous hydrogen. The storage enclosure8 can comprise and/or contain a storage structure 7. The storagestructure 7 can for example be controlled in temperature by heatingmeans 9, for example a heating element, of the system or of theassembly. It is thus possible to ensure a supply and a proportioning ofthe mixing gas at a mixing gas inlet 16 of the device 3, for exampleammonia and/or hydrogen and/or gaseous oxygen. Alternatively or inaddition, the heating means are or comprise for example means or anelement for reheating and/or cooling. The heating means 9 comprise forexample an electrical resistor or a heat exchanger supplied with a heattransfer fluid such as engine coolant liquid.

The heating means 9 allow for example supplying heat directly to theinterior of the storage enclosure 8. Alternatively or in addition, theheating means 9 allow for example transmitting heat from the exterior ofthe enclosure 8 toward the interior of the enclosure 8.

In particular, the heating means 9 allow for example supplying heat tothe storage structure 7.

The storage structure 7 comprises for example a material suited to allowsolid storage of mixing gas. The material comprises for example a salt,such as an alkaline earth salt. The storage structure 7 comprises forexample a layer of storage material, for example at least two layers ofstorage material, the storage material being for example a powderedsalt, that at least two layers of powdered salt being for exampleseparated from one another by at least one layer of a thermallyconductive and/or deformable material.

The layers of the storage structure 7 can have coaxial rotationalsymmetry. The storage structure 7 can for example have a recess withinit, for example along an axis of symmetry of revolution, to provide forstoring and/or removal from storage of mixing gas at each layer of salt.The storage structure 7 can comprise channels for conveying the mixinggas, for example ammonia and/or hydrogen and/or gaseous oxygen, from theexterior of the storage enclosure 8 to the salt layers and/or in theopposite direction.

The heating means 9 can comprise one or more heating modules (notshown), each heating module being adapted to heat one layer of saltindependently of the other heating module(s) and/or independently of theother salt layers.

The storage enclosure 8 is for example connected to a pressure controlelement 6 of the storage and/or mixing gas proportioning enclosure, forexample ammonia and/or hydrogen and/or gaseous oxygen, to the device 3.This element 6 can be controlled by a dedicated electronic controller 10connected to the electronic computer 11 of the engine. In an alternativeconfiguration not shown, the element 6 can be directly controlled by theengine computer 11.

The element 6 is for example a valve, for example a solenoid valve.

The system or the assembly can thus comprise a mixing gas supplycircuit, with for example ammonia and/or hydrogen and/or gaseous oxygen,comprising, from upstream to downstream in the mixing gas circulationdirection, for example the storage enclosure 8, for example the element6, and for example the device 3 for injecting mixing gas into theexhaust.

Device General Structure

With reference to FIGS. 3a-c to 7, a device is described for injectingmixing gas, for example ammonia and/or hydrogen and/or gaseous oxygen,into an exhaust line of exhaust gas of an engine, for example theexhaust line and/or the engine as described above.

The device comprises for example a plurality of walls.

The plurality of walls comprises for example the a wall 31

The device comprises for example one or more inlet openings 311.

The first wall 31 has for example one or more inlet openings 311, forexample the single inlet opening or the totality of inlet openings. Thefirst wall 31 can thus form an inlet wall.

The plurality of walls comprises for example a second wall 32. Thesecond wall 32 has for example one or more outlet openings 321. Thesecond wall is for example positioned downstream of the first wall. Thesecond wall 32 can thus form an outlet wall.

The device comprises for example means 36 for injecting the mixing gas,for example ammonia and/or hydrogen and/or gaseous oxygen. The injectionmeans are for example adapted to allow the injection of mixing gasbetween the first wall and the second wall.

The injection means and/or the plurality of walls and/or the device isor are for example configured so as to allow mixing of the mixing gasand the exhaust gas between the first and the second wall.

The inlet opening(s) can also allow the exhaust gas coming from upstreamin the exhaust line to penetrate into a space comprised between thefirst wall 31 and the second wall 32, where the mixing gas is alsointroduced. The plurality of the walls and the inlet 311 and outlet 321openings allow limiting the space and the fluid circulation at the inletand at the outlet of this space, so as to form a mixing zone. The outletopening(s) 321 can thus allow the mixture of exhaust gas and mixing gasto leave the mixing zone in the direction of the exhaust outlet 17.

Such a device is particularly compact. In particular, it no longernecessitates a mixer downstream of the injection, the injection deviceensuring the mixing of the reducing gas and the exhaust gases. Inaddition, the mixing is particularly effective.

Plurality of Walls

The plurality of walls can comprise at least one intermediate wall, forexample a plurality of intermediate walls. Each intermediate wall is forexample positioned between the first wall 31 and the second wall 32.Each intermediate wall can comprise one or more intermediate opening(s).It is thus possible to adapt the flow between the first wall 31 and thesecond wall 32 to improve the mixing between the mixing gas and theexhaust gases, for example by modulating or by controlling the flow, forexample by limiting the reduction in the gas flow rate. The plurality ofthe intermediate walls can for example comprise a third wall 33comprising one or more intermediate opening(s) 331 and a fourth wall 34comprising one or more intermediate opening(s) 341.

The plurality of walls can thus comprise in all at least three walls,for example four walls, for example five walls, for example more thanfive walls, for example ten walls, for example more than ten walls.

The first wall 31 and/or the second wall 32 and/or the at least oneintermediate wall, for example each wall of the plurality of walls, isfor example separated from the adjacent wall(s) of the plurality ofwalls, for example separated from each other wall of the plurality ofwalls, for example so as to form with each adjacent wall a mixing zone.

The plurality of walls can thus form a stack of walls spaced from oneanother by at least one zone. The zone positioned directly downstream ofthe first wall, for example between the first wall and the second wallin the absence of an intermediate wall, or if not between the first walland the farthest upstream intermediate wall, forms for example the firstzone. In the case where the device comprises at least one intermediatewall, the following zone then forms the second zone, and so on byrecurrence to the n^(th) zone, until the last zone which is the zonebetween the intermediate wall positioned farthest downstream and thesecond wall. Designated by n^(th) zone is thus at least one zonecomprised between the first and the last zone, including the first zoneand the last zone. At least one n^(th) zone forms for example anexchange zone between the exhaust gases entering the device and themixing gas injected into the device.

The first wall 31 and/or the second wall 32 and/or the at least oneintermediate wall, for example each wall of the plurality of walls, cancomprise an upstream face turned upstream, and a downstream face turneddownstream. The upstream face can form an inlet face. The downstreamface can form an outlet face.

The first wall 31 and/or the second wall 32 and the at least oneintermediate wall is for example flat and/or has a flat upstream faceand/or a flat downstream face.

The first wall 31 and/or the second wall 32 and/or the at least oneintermediate wall is for example curved and/or has a curved upstreamface and/or downstream face, for example convex or concave. The firstwall 31 is for example concave, the concavity being turned upstream. Itis thus possible to concentrate the flow of exhaust gases, for exampletoward a central portion of the section of the device and/or of theexhaust line. The second wall 32 is for example concave, the concavitybeing turned downstream. It is thus possible to disperse the flow ofexhaust gases, for example toward the exterior of the section of thedevice and/or of the exhaust line or over the entirety of the samesection.

The first wall 31 and/or the second wall 32 and/or the at least oneintermediate wall, for example each wall of the plurality of walls, hasfor example dimensions strictly smaller than those of the section of theexhaust line, or substantially equal to those of the section of theexhaust line. The exhaust line, for example of a motor vehicle, has forexample a diameter comprised between 25 and 75 mm, for exampleapproximately 50 mm.

The device can lack a lateral wall. In this case, the injection and/ormixing zone is defined by the plurality of walls, which influence theflow of the gases.

Alternatively, the device can also comprise a lateral wall 35. Thelateral wall connects for example the first wall 31 and/or the secondwall 32 and/or at least one intermediate wall, and/or all the walls ofthe plurality of walls. The lateral wall 35 delimits for example, withthe first wall 31 and the second wall 32, an interior space. Thisinterior space is for example the one in which are accomplished theinjection of the mixing gases and the mixing with the exhaust gases.This interior space includes for example at least one n^(th) zone, forexample all the n^(th) zones.

The lateral wall can be distinct from the exhaust line and the devicecomprising means for attaching the device to the exhaust line. In thiscase, the device can have at least in part a smaller section than thatof the section of the exhaust line. The device can then for example havethe shape of a knob.

The device 3 can extend over the entire section of the exhaust line, thelateral wall being for example in contact with the wall of the exhaustline and/or forming or being formed by a portion of the wall of theexhaust line.

The lateral wall is for example substantially cylindrical. The lateralwall has, for example, symmetry of revolution. The lateral wall canhave, in cross section passing through the central axis of the portionof the exhaust line and/or through the axis of the device and/or throughthe axis of symmetry of the lateral wall, a straight and/or convexand/or concave wall.

The device 3 and/or the lateral wall 35 has for example a section, forexample a substantially constant external and/or internal section, i.e.not varying more than 2% in surface.

The device 3 and/or the lateral wall 35 has for example a section, forexample an external and/or internal section, that is strictly increasingor decreasing from upstream to downstream. The device 3 and/or thelateral wall 35 has for example a section in the shape of a truncatedcone.

The device 3 and/or the lateral wall 35 has for example a section, forexample an external and/or internal section, comprising an increasing ordecreasing portion and a substantially constant section, for exampleonly two such portions. The device 3 and/or the lateral wall 35 has forexample a section, for example an external and/or internal section,comprising from upstream to downstream an increasing portion, shaped forexample like a truncated cone, and a substantially constant section. Thelateral wall 35 has for example one or more inlet openings, for examplethe sole inlet opening or the totality of the inlet openings. Thelateral wall 35 can thus form an inlet wall. These inlet openings can bepositioned upstream of the outlet opening(s).

The lateral wall is for example solid and lacking in lateral openings.Alternatively, the lateral wall has for example one or more lateralopening(s) 351. The lateral opening(s) 351 can thus also allow exhaustgases originating upstream of the exhaust line to penetrate into thespace comprised between the first wall 31 and the second wall 32 wherethe mixing gas is also introduced. Alternatively or in addition, the orcertain lateral opening(s) can also allow the mixture of exhaust gas andmixing gas to leave the mixing zone in the direction of the exhaustoutlet 17.

The lateral openings can vary along the lateral wall 35, for examplefrom upstream to downstream. Thus, possibly in combination with theplurality of walls, it is possible to further adapt the flow between thefirst wall 31 and the second wall 32 to improve the mixing between themixing gas and the exhaust gases, for example by modulating orcontrolling the flow, for example by limiting the reduction of the gasflow rate.

The injection device is for example adapted to be positioned in theinterior of the exhaust line, for example so as to allow the passage ofexhaust gas out of the device, for example between the lateral wall andthe wall of the exhaust line. It is thus possible to bring the exhaustgases directly downstream of the device 3, so that they can be mixedthere with the mixture leaving the device 3 and thus form a secondmixing zone downstream of the device 3.

The first wall 31 and/or the second wall 32 and/or the at least oneintermediate wall, for example each wall of the plurality of walls,and/or the lateral wall 35, is for example formed by or comprises aplate.

The first wall 31 and/or the second wall 32 and/or the at least oneintermediate wall, for example each wall of the plurality of walls,and/or the lateral wall 35, is for example made of metal, for example ofstainless steel, for example of a composite material, for example of aceramic, for example coated with a catalytic impregnation for the insitu remediation of the exhaust gases.

Opening

At least one inlet 311 and/or outlet 321 and/or intermediate 331 and/or341 and/or lateral 351 opening, for example each of such opening, can beor comprise a through aperture. In the description, unless the contraryis stated, what is meant by opening is in particular an inlet 311 and/oroutlet 321 and/or intermediate 331 and/or 341 and/or lateral 351opening.

It is for example possible to modify the distribution and shape of theopenings from one wall of the plurality of walls to another and/or alongthe lateral wall and/or from one n^(th) zone to another.

Each inlet 311 and/or outlet 321 and/or intermediate 331 and/or 341and/or lateral 351 opening can have dimensions, for examplesubstantially constant dimensions on the same wall and/or from one wallto another. The dimensions comprise or are for example the diameterand/or the length and/or the width.

The dimensions of at least one opening, for example of each inlet 311and/or outlet 321 and/or intermediate 331 and/or 341 and/or lateral 351opening are for example less than or equal to 5 cm, for example lessthan or equal to 1 cm, for example less than or equal to 5 mm, forexample greater than or equal to 0.05 mm, for example greater than orequal to 0.1 mm, for example greater than or equal to 0.5 mm, forexample on the order of 1mm, for example substantially equal to 1 mm.

For at least one wall of the plurality of walls, the dimensions, forexample the diameter, of the at least one opening can vary, for examplealong a gradient, for example from the center to the periphery.

For example, the dimensions of the openings in a central zone of atleast one wall of the plurality of walls can be greater than or equal,for example strictly greater, than those of a peripheral zone of thesame wall. For example, the dimensions of the openings in a peripheralzone of at least one wall of the plurality of walls can be greater thanor equal, for example strictly greater, than those of a central zone ofthe same wall. In particular, the dimensions of the openings of thiswall can follow an increasing or decreasing gradient from the center tothe periphery.

For example, the plurality of walls can comprise and alternation of oneor more walls of which the dimensions of the openings in a central zoneare greater than or equal, for example strictly greater, than those of aperipheral zone, and of one or more walls of which the diameter of theopenings in a peripheral zone are greater than or equal, for examplestrictly greater, than those of a central zone. For example, theplurality of walls can comprise an alternation of one or more walls ofwhich the diameter of the openings follow an increasing gradient fromthe center to the periphery and of one or more walls of which thedimensions of the openings follow a decreasing gradient from the centerto the periphery.

Alternatively or in addition, the dimensions of the at least one openingof a wall of the plurality of walls, for example of the upstream ofdownstream face of this wall, can vary from one wall to another and/orwith respect to another, at one other at least or at other walls of theplurality of walls, or be substantially the same.

For example, the dimensions of the openings of at least one wall of theplurality of walls can be greater than or equal, for example strictlygreater, than those of the wall immediately upstream. It is thuspossible to facilitate a suction effect and diffusion from upstream todownstream from the openings positioned upstream, which improves thediffusion of the mixing gas and/or of the exhaust gas from upstream todownstream and therefore their mixing.

For example, the dimensions of the openings of each wall of theplurality of walls can be greater than or equal, for example strictlygreater, than those of the wall(s) of the plurality of walls upstream.This can allow a further increase in diffusion.

For example, the dimensions of the openings of at least one wall of theplurality of walls can be less than or equal, for example strictly less,than those of the wall immediately upstream. In this configuration, thedimensions of the apertures diminish from upstream to downstream, whichallows increasing the pressure gradient from upstream to downstream, andthus cause perturbations in the flow and avoid or limit having asubstantial portion of the flow passing directly through the device asif by the effect of a bypass. The perturbed flows thus allow favoringthe mixing of mixing gas and exhaust gas within the device.

For example, the dimensions of the openings of each wall of theplurality of walls can be less than or equal, for example strictly less,than those of the wall(s) of the plurality of walls upstream. This canallow a further increase in the levels of turbulence via in particularthe establishment of numerous recirculation zones.

For one wall of the plurality of walls, or a portion of said wall, atotal empty surface is defined. The total empty surface can be definedas the surface occupied by the opening(s) of a wall, or of a portion ofsaid wall, on the upstream face or the downstream face, or the averageof these measured surfaces for the upstream face and the downstreamface.

For one wall of the plurality of walls, or a portion of said wall, atotal empty surface density is defined. The total empty surface densitycan be defined as the ratio of the surface occupied by the opening(s) ofa wall, or of a portion of said wall, on the upstream face or thedownstream face, or the average of these measured surfaces for theupstream face and the downstream face, with respect to the surfaceoccupied by material at the upstream face or the downstream face, or theaverage of these measured surfaces for the upstream and downstreamfaces.

For one wall of the plurality of walls, or a portion of said wall, atotal empty volume density is defined. The total empty volume densitycan be defined as the ratio of the volume occupied by the opening(s) ofa wall, or of a portion of said wall, with respect to the volumeoccupied by material.

For one wall of the plurality of walls, or a portion of said wall, thenumber of distinct openings is defined as the quantity of openings.

For at least one wall of the plurality of walls, the total empty surfaceand/or the total empty surface density and/or the total empty volumedensity and/or the quantity of openings can vary, for example along agradient, for example from the center to the periphery.

For example, the total empty surface and/or the total empty surfacedensity and/or the total empty volume density and/or the quantity ofopenings in a central zone of at least one wall of the plurality ofwalls can be greater than or equal, for example strictly greater, thanthat of a peripheral zone of the same wall. The central zone is fartheraway from the periphery than the peripheral zone, for example thecentral zone is included in the smallest solid surface comprising theperipheral zone on the wall under consideration. The central and/orperipheral zone is for example an annular zone. For example the totalempty surface and/or the total empty surface density and/or the totalempty volume density and/or the quantity of openings in a peripheralzone of at least one wall of the plurality of walls can be greater thanor equal, for example strictly greater, than that of a central zone ofthe same wall. In particular, the total empty surface and/or the totalempty surface density and/or the total empty volume density and/or thequantity of openings of this wall can follow an increasing or decreasinggradient from the center to the periphery.

For example, the plurality of wall can comprise an alternation of one ormore walls of which the total empty surface and/or the total emptysurface density and/or the total empty volume density and/or thequantity of openings in a central zone is greater than or equal, forexample strictly greater, than that of a peripheral zone, and of one ormore walls of which the total empty surface and/or the total emptysurface density and/or the total empty volume density and/or thequantity of openings in a peripheral zone is greater than or equal, forexample strictly greater, than that of a central zone. It is thuspossible, as illustrated in FIG. 5, to create currents alternatelytoward the center and toward the periphery of the device and/or of theexhaust line, which allows still better mixing and an extension of thedistance over which the mixing takes place. For example, the pluralityof walls can comprise an alternation of one or more walls of which thetotal empty surface and/or the total empty surface density and/or thetotal empty volume density and/or the quantity of openings follows anincreasing gradient from the center to the periphery and one or morewalls of which the total empty surface and/or the total empty surfacedensity and/or the total empty volume density and/or the quantity ofopenings follows a decreasing gradient from the center to the periphery.

For example, the total empty surface and/or the total empty surfacedensity and/or the total empty volume density and/or the quantity ofopenings of at least one wall of the plurality of walls can be greaterthan or equal, for example strictly greater, than that of the wallimmediately upstream. It is thus possible to facilitate a suction effectand diffusion from upstream to downstream from the openings positionedupstream, which improves the diffusion of mixing gas and/or exhaust gasfrom upstream to downstream and therefore their mixing.

For example, the total empty surface and/or the total empty surfacedensity and/or the total empty volume density and/or the quantity ofopenings of each wall of the plurality of walls can be greater than orequal, for example strictly greater, than that of the wall(s) of theplurality of walls upstream. This can allow a further increase indiffusion.

For example, the total empty surface and/or the total empty surfacedensity and/or the total empty volume density and/or the quantity ofopenings of each wall of the plurality of walls can be less than orequal, for example strictly less, than that of the wall immediatelyupstream. In this configuration, the pressure gradient can increase fromupstream to downstream, and thus cause perturbations in the flow andavoid or limit the fact that a substantial part of the flow passesdirectly through the device as if by the effect of a bypass. Theperturbed flows thus allow favoring the mixing of mixing gas and of theexhaust gases within the device.

For example, the total empty surface and/or the total empty surfacedensity and/or the total empty volume density and/or the quantity ofopenings of each wall of the plurality of walls can be less than orequal, for example strictly less, than that of the wall(s) of theplurality of walls upstream. This allows a further increase in theperturbations.

With reference to FIGS. 6a to 6c , one wall of the plurality of wallscan comprise a central portion, substantially elongated for example,ovoid for example.

The wall can also comprise at least one radial portion, for example aplurality of radial portions 621, 622, 623, 624, extending from thecentral portion to the periphery. The radial portion is for example anarm, for example a segment. The radial portion is for example straight.The wall can for example comprise one, two, three or four radialportions perpendicular or parallel to one another, two by two.

The wall can comprise at least one peripheral portion 63, for exampleseveral peripheral portions 63, extending around the central portion 61,for example without discontinuity, for example so as to form an annularstrip, for example defining an elongated shape, ovoid for example. Eachperipheral portion 63 comprises for example a plurality of sections 631,632, 633, 634, curved sections for example, connecting different radialportions. The peripheral portions can form different annular stripsincluded inside one another.

The central portion 61 and/or the at least one radial portion and/or theat least one peripheral portion 63 are for example arranged so as toform between them the opening(s) of the wall under consideration.

With reference to FIG. 6a , the dimensions of the openings of this wallcan follow an increasing gradient from the center to the periphery, thetotal empty surface and/or the total empty surface density and/or thetotal empty volume density can vary according to an increasing gradientfrom the center to the periphery. In particular, the spacing between theperipheral portions can follow an increasing gradient from the center tothe periphery.

With reference to FIG. 6b , the spacing between the peripheral portioncan follow a decreasing gradient from the center to the periphery.

With reference to FIG. 6c , the spacing between the peripheral portionscan remain constant from the center to the periphery.

As illustrated in FIGS. 3b and 3c , at least one portion of the openingsof a wall of the plurality of walls, for example all the openings ofsuch a wall, are for example distributed in concentric circles.

From one wall to another, at least one portion of the openings of thewalls of the plurality of walls is for example offset so as to modulatethe flow.

Catalyst

The device can comprise a catalyst positioned in at least one nth zone,for example at least the last zone. The first wall 31 and/or the secondwall 32 and/or the at least on intermediate wall, for example each wallof the plurality of walls, and/or the lateral wall 35, can be coated atleast partially by a washcoat, the washcoat comprising for example aporous structure, the washcoat supporting a catalyst and/or the catalystimpregnating the washcoat, for example an SCR catalyst and/or anoxidation catalyst. It is thus possible for the device to provide an SCRcatalytic conversion function and thus to eliminate or reduce in sizethe possible SCR catalytic converter positioned downstream. The catalystcan form a washcoat. The catalyst can coat at least one wall face turnedtoward the interior of the device, i.e. a wall face which is not theface turned toward the exterior of the first wall 31, the second wall 32or the lateral wall 35, which in particular is not the upstream face ofthe first wall 31, the downstream face of the second wall 32 or theexterior face of the lateral wall 35. The zone at which the catalyst ispositioned can thus form an SCR catalytic converter.

Bypass

The device can comprise means for bypassing, i.e. deriving, at least then^(th) zone, for example a plurality of n^(th) zones, at one opening atleast, configured to form a fluid communication between at least oneopening of a wall of the plurality of walls upstream of the nth zonewith at least one opening of a wall of the plurality of walls downstreamof the nth zone without passing through the nth zone. The device cancomprise a plurality of such means for bypassing the same nth zone ordifferent nth zones. Such means for bypassing allow limiting the mixingin one zone to a portion of the flow, the other portion of the flowbeing reinjected only into a zone of the device situated downstream, ordownstream of the device, to be mixed downstream.

The device can comprise means for bypassing or deriving the first zoneand/or the second zone and/or the third zone and/or the nth zone and/orthe last zone.

The bypass means comprise for example a duct, for example a tube,connecting the upstream opening and the downstream opening.

Injection Means

The injection means 36 comprise for example an injector, for example amultipoint injector. The injection means 36 comprise for example onebranch, for example several branches. Each branch has for example oneopening, for example a plurality of openings.

The injection means 36 are for example positioned, for example at leastin part, at for example a central portion of the first wall 31 and/or ofthe second wall 32. It is thus possible to inject the mixing gas at acentral section of the device.

The injection means are for example adapted to inject the mixing gasbetween the first wall 31 and an intermediate wall, for example theintermediate wall farthest upstream, for example the intermediate wallimmediately downstream of the first wall 31. It is thus possible to forma first chamber of the device, for example the first zone, adapted forinjection and a possible first mixing, and a second chamber of thedevice positioned downstream, for example downstream of the first zone,for more thorough mixing.

The injection means are for example adapted for injecting mixing gasinto a plurality of nth zones, the injection varying for example fromone zone to another, for example in terms of flow.

Alternatively or in addition, the injection means 36 are for examplepositioned, for example at least in part, at the lateral wall 35. Thisallows for example simplifying the injection or limiting the quantity ofmaterial necessary for its manufacture.

The injection means 36 may not extend, or may not substantially extendbetween the first wall 31 and the second wall 32. The injection means 36can thus comprise one or more aperture(s) leading to the first wall 31and/or the second wall 32 and/or the lateral wall 35.

Alternatively or in addition, the injection means 36 can extend betweenthe first wall 31 and the second wall 32. The injection means 36 can forexample extend in or along an intermediate wall. The injection means 36can for example comprise an injection portion extending between thefirst wall 31 and the second wall 32. The injection portion comprisesfor example a perforated tube or a plurality of perforated tubes. Eachperforated tube may comprise at least one aperture for injecting mixinggas, for example ammonia and/or hydrogen and/or gaseous oxygen, forexample a plurality of apertures for injecting mixing gas.

The injection means 36 can for example extend from a central portionand/or from the center of the first wall 31 and/or of the second wall32.

The device 3 and/or the exhaust line and/or the system can comprisesupply means 361 for mixing gas, for example ammonia and/or hydrogenand/or gaseous oxygen, of the injection means. The supply means 361comprise for example a supply duct.

Attachment

The device comprises for example means of attachment to the exhaust lineand/or to the system, for example means for attachment to the wall ofthe exhaust line.

The attachment means comprise for example the injection means and/or thesupply means.

The attachment means comprise for example means for attachment to thefirst wall and/or the second wall and/or at least one intermediate wall,for example positioned at the periphery of this wall or of these walls.

The first wall 31 and/or the second wall 32 and/or at least oneintermediate wall is for example connected and/or attached to anotherwall of the plurality of walls by connection and/or attachment meansbetween dedicated walls, these means being for example distinct from thelateral wall 35. The connection and/or attachment means between wallscomprise for example a connection and/or attachment wall, for example incontact with and/or attached to a central portion of each connectedand/or attached wall. The connection wall forms for example a tube. Theattachment means of the device are for example in contact withattachment and/or connection means between walls to provide for theattachment of the device.

Examples of Devices

With reference to FIGS. 3a to 3c , such a device 3 is described. Thearrow in FIG. 3a shows the flow direction. The first wall 31 and thesecond wall 32 are for example flat.

The first wall 31 and the second wall 32 have for example dimensionsstrictly smaller than those of the section of the exhaust line. Theinjection device is for example adapted to be positioned in the interiorof the exhaust line, for example so as to allow passage of exhaust gasout of the device, for example between the lateral wall and the wall ofthe exhaust line.

The device can also comprise a lateral wall 35. The lateral wallconnects for example the first wall 31 and the second wall 32. Thelateral wall 35 delimits for example with the first wall 31 and thesecond wall 32 an interior space. This interior space is for examplethat in which are accomplished the injection of mixing gas and mixingwith the exhaust gases. This interior space includes for example thefirst zone. The lateral wall can be distinct from the exhaust line andthe device comprising the means for attaching the device to the exhaustline. In this case, the device can have at least in part a smallersection than that of the section of the exhaust line. The device canhave for example the shape of a knob. The lateral wall is for examplesubstantially cylindrical. The lateral wall has for example symmetry ofrevolution. The device 3 and the lateral wall 35 have for example adecreasing section.

Each wall of the plurality of walls is for example formed by orcomprises a plate, of metal for example.

Each inlet 311 and/or outlet 321 opening can be a through aperture.

The total empty surface and/or the total empty surface density and/orthe total empty volume density and/or the quantity of openings of thesecond wall can be strictly greater than that of the first wall. Thefirst wall 31 can comprise fewer than twenty inlet openings 311, forexample fewer than ten openings. The second wall 32 can comprise atleast forty, for example at least fifty, for example at least sixtyoutlet openings 321.

The injection means 36 comprise for example an injector. The injectionmeans 36 are for example positioned at a central portion of the firstwall 31. The injection means 36 may not extend between the first wall 31and the second wall 32. The device 3 and/or the exhaust line and/or thesystem can comprise mixing gas supply means 361 of the injection means.The injection means 361 comprise for example a supply duct.

The attachment means comprise for example the injection means and/or thesupply means.

With reference to FIG. 4, another of such device 3 is described. Thearrows in FIG. 4 show the flow direction and the flow lines. The firstwall 31 and the second wall 32 are for example curved, for exampleconvex or concave. The first wall 31 is for example concave, theconcavity being turned upstream. It is thus possible to concentrate theflow of exhaust gases, for example toward a central portion of thesection of the device and/or of the exhaust line. The second wall 31 isfor example concave, the concavity being turned downstream. It is thuspossible to disperse the flow of exhaust gases, for example toward theoutside of the section of the device and/or of the exhaust line or overthis entire section.

The first wall 31 and the second wall 32 have for example dimensionsstrictly smaller than those of the section of the exhaust line. Theinjection device is for example adapted to be positioned inside theexhaust line, for example so as to allow the passage of exhaust gasesout of the device, for example between the lateral wall and the wall ofthe exhaust line.

The device can also comprise a lateral wall 35. The lateral wallconnects for example the first wall 31 and the second wall 32. Thelateral wall 35 delimits for example, with the first wall 31 and thesecond wall 32, an interior space. This interior space is for examplethat in which are accomplished the injection of mixing gas and mixingwith the exhaust gases. This interior space includes for example thefirst zone. The lateral wall can be distinct from the exhaust line andthe device comprising means for attaching the device to the exhaustline. In this case, the device can have at least in part a sectionsmaller than that of the section of the exhaust line. The device canthen have for example the shape of a knob. The lateral wall is forexample substantially cylindrical. The lateral wall has for examplesymmetry of revolution. The lateral wall can have, in cross sectionpassing through the axis of the device and/or through the axis ofsymmetry of the lateral wall, a straight wall. The device 3 and thelateral wall 35 have for example a substantially constant section. Thelateral wall has for example several lateral openings 351.

Each wall of the plurality of walls is for example formed by orcomprises a plate, of metal for example.

Each inlet 311 and/or outlet 321 and/or lateral 351 opening can be athrough aperture.

Each inlet 311 and/or outlet 321 and/or intermediate 331 and/or 341and/or lateral 351 opening can have substantially constant dimensions.

The injection means 36 comprise for example an injector. The injectionmeans 36 can extend between the first wall 31 and the second wall 32.The injection means can for example comprise an injection portionextending between the first wall 31 and the second wall 32. Theinjection portion comprises for example a perforated tube. The device 3and/or the exhaust line and/or the system can comprise mixing gas supplymeans 361 of the injection means. The supply means 361 comprise forexample a supply duct.

The attachment means comprise for example the injection means and/or thesupply means.

With reference to FIG. 5, yet another of such device 3 is described. Thearrows in FIG. 5 show the flow direction and the lines of flow. Thedevice 3 can comprise a plurality of intermediate walls. Eachintermediate wall is for example positioned between the first wall 31and the second wall 32. Each intermediate wall can comprise serveralintermediate openings. It is thus possible to adapt the flow between thefirst wall 31 and the second wall 32 to improve the mixing between themixing gas and the exhaust gases, for example by modulating or bycontrolling the flow, for example by limiting the reduction in the gasflow rate. The plurality of intermediate walls can for example comprisea third wall 33 comprising several intermediate openings 331 and afourth wall 34 comprising several intermediate opening(s) 341.

The plurality of walls can also comprise in total at least four walls,for example exactly four walls.

The first wall 31, the second wall 32 and the intermediate walls 33 and34 are for example flat.

The first wall 31 and the second wall 32 have for example dimensionssubstantially equal to those of the section of the exhaust line. Theinjection device can extend over the entire section of the exhaust line.

The device can also comprise a lateral wall 35. The lateral wallconnects for example the first wall 31, the second wall 32 and the twointermediate walls 33 and 34. The lateral wall 35 delimits for example,with the first wall 31 and the second wall 32, an interior space. Thisinterior space is for example the one in which are accomplished theinjection of mixing gas and the mixing with the exhaust gases. Thisinterior space includes for example the first, second and third zones.The device 3 can extend over the entire section of the exhaust line, thelateral wall 35 being formed by a portion of the wall of the exhaustline. The lateral wall is for example substantially cylindrical. Thelateral wall has for example symmetry of revolution. The lateral wallcan have, in cross section passing through the central axis of theportion of the exhaust line, the axis of the device and/or through theaxis of symmetry of the lateral wall, a straight wall. The device 3 andthe lateral wall 35 have for example a substantially constant section.

Each wall of the plurality of walls and the lateral wall 35 are forexample formed or each comprise a plate, of metal for example.

The plurality of walls can comprise an alternation of one or more wallsthe diameters of the openings of which follow an increasing gradientfrom the center to the periphery, for example the intermediate wall 33and/or the second wall 32 and of one or more walls the diameters of theopenings of which follow a decreasing gradient from the center to theperiphery, for example the first wall 31 and/or the intermediate wall34.

Alternatively or in addition, the plurality of walls can comprise andalternation of one or more walls of which the total empty surface and/orthe total empty surface density and/or the total empty volume densityand/or the quantity of openings follows an increasing gradient from thecenter to the periphery, for example the intermediate wall 33 and/or thesecond wall 32 and of one or more walls of which the total empty surfaceand/or the total empty surface density and/or the total empty volumedensity and/or the quantity of openings follows a decreasing gradientfrom the center to the periphery, for example the first wall 31 and theintermediate wall 34.

The injection means 36 comprise for example and injector. The injectionmeans are for example adapted to inject the mixing gas, for exampleammonia and/or hydrogen and/or gaseous oxygen, between the first wall 31and the intermediate wall 33 immediately downstream of the first wall31. The injection means 36 are for example positioned at the lateralwall 35. The injection means 36 may not extend between the first wall 31and the second wall 32. The injection means can thus comprise a throughaperture leading to the lateral wall 35.

With reference to FIG. 7, still another of such device 3 is described.The arrows in FIG. 7 show the flow direction and the lines of flow. Thedevice 3 can comprise a plurality of intermediate walls. Eachintermediate wall is for example positioned between the first wall 31and the second wall 32. Each intermediate wall can comprise serverintermediate openings. It is thus possible to adapt the flow between thefirst wall 31 and the second wall 32 to improve the mixing between themixing gas and the exhaust gases, for example by modulating or bycontrolling the flow, for example by limiting the reduction of the gasflow rate. The plurality of intermediate wall can for example comprise athird wall 33 comprising several intermediate openings 331 and a fourthwall 34 comprising several intermediate opening(s) 341.

The plurality of walls can also comprise in total at least four wall,for example exactly four walls.

The first wall 31, the second wall 32 and the intermediate walls 33 and34 are for example flat.

The first wall 31 and the second wall 32 have for example dimensionssubstantially equal to those of the section of the exhaust line. Theinjection device can extend over the entire section of the exhaust line.

The device can also comprise a lateral wall 35. The lateral wallconnects for example the first wall 31, the second wall 32 and the twointermediate walls 33 and 34. The lateral wall 35 delimits for example,with the first wall 31 and the second wall 32, an interior space. Thisinterior space is for example that in which are accomplished theinjection of mixing gas and mixing with the exhaust gases. This interiorspace includes for example the first, second and third zones. The device3 can extend over the entire section of the exhaust line, the lateralwall 35 being formed by a portion of the wall of the exhaust line. Thelateral wall is for example substantially cylindrical. The lateral wallhas for example symmetry of revolution. The lateral wall can have, incross section passing through the central axis of the portion of theexhaust line of the device and/or through the axis of symmetry of thelateral wall, a straight wall. The device 3 and the lateral wall 35 havefor example a substantially constant section.

Each wall of the plurality of walls and the lateral wall 35 are forexample formed or each comprise a plate, of metal for example.

From upstream to downstream, the openings of the walls of the pluralityof walls become smaller and smaller and more numerous, without howevercovering a larger surface. Thus, the dimensions of the openings of eachwall of the plurality of walls can be less than or equal, for examplestrictly less, than those of the wall(s) of the plurality of wallsupstream. The total empty surface and/or the total empty surface densityand/or the total empty volume density of each wall of the plurality ofwalls can be strictly less than that of the walls of the plurality ofwalls upstream. The quantity of openings of each wall of the pluralityof walls can be strictly greater than that of the walls of the pluralityof walls upstream.

The device can comprise means for bypassing or deriving the first zoneonly. The device can comprise means for bypassing or deriving the firstand the second zones only. The device can comprise means for bypassingthe first, the second and the third zones. The bypass means comprise forexample a duct, for example a tube, connecting the upstream opening andthe downstream opening.

The injection means 36 comprise for example an injector. The injectionmeans are for example adapted to inject the mixing gas, for exampleammonia and/or hydrogen and/or gaseous oxygen, between the first wall 31and the intermediate wall 33 immediately downstream of the first wall31. The injection means are for example positioned at the lateral wall35. The injection means 36 may not extend between the first wall 31 andthe second wall 32. The injection means can thus comprise an apertureleading to the lateral wall 35.

Method

With reference to FIG. 8, a method of injecting mixing gas, for exampleammonia and/or hydrogen and/or gaseous oxygen, into an exhaust gasexhaust line of an engine implemented by means of a device 3 asdescribed above.

The method comprises for example a first step 801 of entering exhaustgases between the first wall 31 and the second wall 32, for example byat least one inlet opening 311 of the first wall. The exhaust gases thuspenetrate into the injection and mixing zone, for example with a flowmodified by at least one inlet opening 311 and/or the shape of the inletwall 31.

The method comprises for example a second step 802 of injecting mixinggas, for example ammonia and/or hydrogen and/or gaseous oxygen, betweenthe first wall 31 and the second wall 32. It is thus possible to placein contact, in the same space, the exhaust gas and the mixing gas.

The method comprises for example a third step 803 of mixing the enteringexhaust gases and the injected mixing gas. Effective mixing directlyduring injection is allowed by the structure of the device whichdelimits a mixing zone.

The method comprises for example a fourth step 804 of output mixedexhaust and mixing gas by at least one opening of the second wall. It isthus possible to obtain a homogeneous mixture of mixing gas and exhaustgases, which no longer necessitates additional mixing or which willrequire a mixer with reduced dimensions.

1. A device for injecting a mixing gas into an exhaust gas exhaust lineof an engine, the device comprising: one or more inlet openings, aplurality of walls comprising: a first wall, and a second wall havingone or more outlet openings and positioned downstream of the first wall,and injection means of the mixing gas between the first wall and thesecond wall, so as to allow mixing of the mixing gas and the exhaustgases between the first wall and the second wall.
 2. The deviceaccording to claim 1, wherein the plurality of walls comprises at leastone intermediate wall positioned between the first wall and the secondwall, the intermediate wall comprising one or more openings.
 3. Thedevice according to claim 1, comprising means for bypassing at least onezone, at one opening at least, configured to form a fluid communicationbetween at least one opening of a wall of the plurality of wallsupstream of the zone with at least one opening of a wall of theplurality of walls downstream of the zone without passing through thezone.
 4. The device according to claim 1, also comprising a lateral wallconnecting the first wall and the second wall and delimiting with thefirst wall and the second wall an interior space, the injection devicebeing adapted to be positioned inside the exhaust line, so as to allowthe passage of exhaust gases between the lateral wall and the wall ofthe exhaust line.
 5. The device according to claim 4, wherein the devicecomprises means for attaching the device to the exhaust line.
 6. Thedevice according to claim 1, the device forming a section of the exhaustline, in particular the device comprising a lateral wall connecting thefirst wall and the second wall and delimiting with the first wall andthe second wall an interior space so that the lateral wall is in contactwith the exhaust line and/or forms a portion of the wall of the exhaustline.
 7. The device according to claim 5, comprising mixing gas supplymeans of the injection means, the attachment means comprising the supplymeans.
 8. The device according to claim 1, wherein the first wall or thelateral wall has one or more of the one or more inlet openings.
 9. Thedevice according to claim 1, wherein the injection means are positionedat the first wall or extend between the first wall and the second wallfrom the first wall.
 10. The device according to claim 1, wherein, forat least one wall of the plurality of walls, the dimensions of theopenings or the total empty surface or the total empty surface densityor the total empty volume density or the quantity of openings vary(ies).11. The device according to claim 1, wherein the dimensions of theopenings or the total empty surface or the total empty surface densityor the total empty volume density or the quantity of openings of atleast one wall vary(ies) with respect to at least one other wall of theplurality of walls.
 12. An assembly comprising an engine and/or anexhaust gas exhaust line of the engine, the assembly comprising a deviceaccording claim
 1. 13. The assembly according to claim 12, comprising aselective catalytic reduction system for exhaust gases, or an oxidationcatalyst.
 14. A method for injecting a mixing gas into an exhaust gasexhaust line of an engine implemented by means of a device according toclaim 1, comprising the following steps: entry of the exhaust gasesbetween the first wall and the second wall, injection of the mixing gasbetween the first wall and the second wall, mixing the entered exhaustgases and the injected mixing gas, output of the mixed exhaust gases andthe mixing gas by at least one opening of the second wall.